Iodoalkoxylation of 1,5-anhydro-2-deoxy-hex-1-enitols (glycals).
Exclusive trans-addition is observed in the iodoalkoxylation of the 6-membered cyclic enol ethers 3,4-di-O-acetyl-L-rhamnal (1), 3,4-di-O-acetyl-L-fucal (2), and related glycal derivatives. The main products from 1 and from 3,4,6-tri-O-acetyl-D-glucal (3) thus had the alpha-manno configuration. Similarly, alpha-talo products were obtained from 2 in 87-93% yield. The product distribution is not affected by the electronegativity of the 5-substituent. It is concluded that steric factors in the glycal and the nucleophile affect only the step of trans-diaxial opening of the intermediate iodonium ion. Enhanced yields of the desired trans-diaxial products were observed in reactions of glycals having the lyxo configuration when the reactions were conducted in tetrahydrofuran or methanol.
Horton
D
D
Department of Chemistry, Ohio State University, Columbus 43210.
Priebe
W
W
Sznaidman
M
M
D000478:Alkylation; D003837:Deoxy Sugars / Q000138:chemical synthesis* / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013237:Stereoisomerism; D013402:Sugar Alcohols / Q000138:chemical synthesis* / Q000737:chemistry
D003837:Deoxy Sugars; D013402:Sugar Alcohols